DE 10 2007 023 409 A1 has disclosed a backpack sprayer having a container for spraying agent. The container for spraying agent is configured as a blow-molded part and has an approximately rectangular cross section. A screw lid which is placed onto a round filling opening is arranged on the upper side of the container. The cross-sectional area of the filling opening is considerably smaller than the greatest inner cross-sectional area of the container for spraying agent. In customary containers for spraying agent having a screw lid, the area of the filling opening is considerably smaller than 50% of the greatest horizontal inner cross-sectional area of the container. The filling of spraying agent and the cleaning of the container can be made difficult as a result.